Transcript Identical Versus Fraternal Twins

Myers’ Psychology for AP*
David G. Myers
*AP is a trademark registered and/or owned by the College Board, which was not involved in the production of, and does not endorse, this product.
Unit 3C:
Biological Bases of Behavior:
Genetics, Evolutionary
Psychology, and Behavior
Unit Overview
• Behavior Genetics: Predicting Individual
Differences
• Evolutionary Psychology:
Understanding Human
Nature
• Reflections on Nature and
Nurture
Click on the any of the above hyperlinks to go to that section in the presentation.
Behavior Genetics: Predicting
Individual Differences
Introduction
• Behavior genetics
–Heredity versus the environment
Genes: Our Codes for Life
• Chromosome
• DNA (deoxyribonucleic acid)
• Genes
–Active (expressed)
vs. inactive
• Genome
Twin and Adoption Studies
Identical Versus Fraternal Twins
• Identical twins
• Fraternal twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Identical Versus Fraternal Twins
Twin and Adoption Studies
Separated Twins
• U of MN studies on identical twins
separated at birth
• Anecdotal evidence
• “Virtual twins”
Twin and Adoption Studies
Biological Versus Adoptive Relatives
• Genetic relatives
• Environmental relatives
Heritability
• Heritability
–“difference among people”
Heritability
Group Differences
• Heritable differences between
individuals does not imply
heritable group differences
Heritability
Nature and Nurture
• Influence of adaptation
• Nature and nurture work together
• Genes are
self-regulating
Gene-Environment Interaction
• Genes and experience interact
–Evocative interactions
The New Frontier: Molecular
Genetics
• Molecular genetics
–Molecular behavior genetics
–Genetics and diseases
Evolutionary Psychology:
Understanding Human Nature
Natural Selection and Adaptation
• Evolutionary psychology
–Natural selection
• Mutation
• Adaptation
• Fitness
Evolutionary Success Helps Explain
Similarities
• Behaviors that contribute to
survival are found throughout
cultures
Evolutionary Success Helps Explain Similarities
Outdated Tendencies
• Genetic traits which helped our
ancestors survive may harm us
today
Evolutionary Success Helps Explain Similarities
Evolutionary Psychology Today
• “the Second Darwinian Revolution”
An Evolutionary Explanation of Human Sexuality
Gender Differences in Sexuality
• Studies suggesting men have a
stronger tendency towards sex
An Evolutionary Explanation of Human Sexuality
Natural Selection and Mating Preferences
• Differing preferences in partners
–Male preferences
–Female preferences
Critiquing the Evolutionary
Perspective
• Backward theorizing
• Impact of social influence
Reflections on Nature and
Nurture
The End
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Definition
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Behavior genetics
= the study of the relative power and limits of
genetic and environmental influences on
behavior.
Environment
= every non-genetic influence, from prenatal
nutrition to the people and things around
us.
Chromosomes
= threadlike structures made of DNA
molecules that contain the genes.
DNA (deoxyribonucleic acid)
= a complex molecule containing the genetic
information that makes up the
chromosomes.
Genes
= the biochemical units of heredity that make
up the chromosomes; segments of DNA
capable of synthesizing a protein.
Genome
= the complete instructions for making an
organism, consisting of all the genetic
material in that organism’s chromosomes.
Identical Twins
= twins who develop from a single fertilized
egg that splits in two, creating two
genetically identical organisms.
Fraternal Twins
= twins who develop from separate fertilized
eggs. They are genetically no closer than
brothers and sisters, but they share a fetal
environment.
Heritability
= the proportion of variation among
individuals that we can attribute to genes.
The heritability of a trait may vary,
depending on the range of populations
and environments studied.
Interaction
= the interplay that occurs when the effect of
one factor (such as environment) depends
on another factor (such as heredity).
Molecular Genetics
= the subfield of biology that studies the
molecular structure and function of genes.
Evolutionary Psychology
= the study of the evolution of behavior and
the mind,using principles of natural
selection.
Natural Selection
= the principle that, among the range of
inherited trait variations, those that lead to
increased reproduction and survival will
most likely be passed on to succeeding
generations.
Mutation
= the random error in gene replication that
leads to a change.